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Main Authors: Navarro, Julia, Wilkinson, Mark
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2605.27679
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author Navarro, Julia
Wilkinson, Mark
author_facet Navarro, Julia
Wilkinson, Mark
contents We construct and evaluate group-equivariant neural networks for the prediction of the two-dimensional $Q$-tensor order parameter of nematic liquid crystals from synthetically generated microscopic textures. Seven architectures, equivariant to cyclic groups $C_k$ of order $k$ for $k=4,\,8,\,16,\,32,\,64,\,128,\, 256$, are built using a combination of weight-sharing constraints, equivariant activations and regularization techniques. To do this, we construct rotation-like permutation matrix groups with elements $\varrho_{C_k}(g)$ that act on row-wise vectorized images, thereby approximating a $\frac{2π}{k}$ rotation of the circular subdomain on square images. We show that all seven equivariant models satisfy the $Q$-tensor equivariance constraint to within single-precision floating point accuracy. Comparing against approximate parameter-matched non-equivariant benchmarks, with and without data augmentation, we find that the equivariant models consistently achieve lower errors and generalize more robustly to unseen defect configurations. Performance increases with group order, suggesting that the incorporation of finer rotational symmetry leads to lower errors.
format Preprint
id arxiv_https___arxiv_org_abs_2605_27679
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the Equivariant Learning of the $Q$-tensor Order Parameter
Navarro, Julia
Wilkinson, Mark
Soft Condensed Matter
Computer Vision and Pattern Recognition
Machine Learning
76A15 (Primary), 68T07, 82D03, 20C35 (Secondary)
We construct and evaluate group-equivariant neural networks for the prediction of the two-dimensional $Q$-tensor order parameter of nematic liquid crystals from synthetically generated microscopic textures. Seven architectures, equivariant to cyclic groups $C_k$ of order $k$ for $k=4,\,8,\,16,\,32,\,64,\,128,\, 256$, are built using a combination of weight-sharing constraints, equivariant activations and regularization techniques. To do this, we construct rotation-like permutation matrix groups with elements $\varrho_{C_k}(g)$ that act on row-wise vectorized images, thereby approximating a $\frac{2π}{k}$ rotation of the circular subdomain on square images. We show that all seven equivariant models satisfy the $Q$-tensor equivariance constraint to within single-precision floating point accuracy. Comparing against approximate parameter-matched non-equivariant benchmarks, with and without data augmentation, we find that the equivariant models consistently achieve lower errors and generalize more robustly to unseen defect configurations. Performance increases with group order, suggesting that the incorporation of finer rotational symmetry leads to lower errors.
title On the Equivariant Learning of the $Q$-tensor Order Parameter
topic Soft Condensed Matter
Computer Vision and Pattern Recognition
Machine Learning
76A15 (Primary), 68T07, 82D03, 20C35 (Secondary)
url https://arxiv.org/abs/2605.27679